With energy declining and energy demands rising, the need for heating and cooling systems independent or nearly independent of central electrical power sources becomes ever-increasing. Heretofore, some success has been obtained with solar heat; but a major disadvantage in solar heating systems for shelters is that demands for heat and/or cold in the shelter is the heaviest when the supply of solar energy is at it's natural ebb. Heat from the sun must be stored for use when the sun is not shining. Wind, as a source of energy cannot be depended upon as a source of heat during periods of calm. The wind and sun are indeed weather-sensitive energy sources. A source of energy which is not weather sensitive may become weather-sensitive to a certain extent, by the harnessing means employed. For example, an evaporator-condensor system which takes heat from the outside atmosphere, releasing it into the shelter, will operate more efficiently during the day when the outside temperature is much lower.
Convenience controlled non-weather-sensitive heat sources are not always available on a constant basis. For example, a fireplace may be conveniently operated for only three hours during most evenings. An oven may operate for another two hours. An incinerator for disposal of trash or garbage, may operate for yet another hour. Ultimately, all or most of these readily available "controlled" heat sources should be fully utilized in home air conditioning systems without significant loss of heat to the outside atmosphere or into the ground through complicated heat transmission systems; and it is desirable, if not essential, to maximize the efficiency of these controlled heat sources and to eliminate unnecessary transmission lines, fans, pumps, coils and the like.
To permit continuity of air conditioning, therefore, through periods of low energy-producing weather and inconvenient controlled heat operation, weather-sensitive sources and convenience-controlled non weather-sensitive sources should have a heat and/or cold storage facility. This facility, in order to provide maximum efficiency should be integrated as closely as possible with the means of producing the heat or cold and the living space in which the heat or cold will be ultimately employed. The more fully the integration is accomplished, the more practical and efficient will be the system, because a fully integrated system inevitably eliminates losses of heat storage and transmission losses and the inevitable expense and probable power drain involved in heat transmission. A direct heat transfer relationship, for example, between a fireplace and the heat storage medium and between the heat storage medium and the living space would logically provide the most efficient system for using the fireplace for heating during periods in which it is inconvenient to tend a fire. While it may not be possible to fully integrate solar heat collecting units with the heat storage facility, it may yet be possible to integrate by direct heat transfer the heat storage facility with the living space.
A separate but overlapping consideration is that while the best of integrated systems may involve several heat sources at least some of which depend upon pumps, fans, etc., requiring constant energy sources, it is most desirable that efficient home heating be at least minimally operable in the absence of outside central electrical power sources, and during weather negating periods in which the sun is not shining or the wind is not blowing.
The teachings of the prior art have not fully utilized the principal of integration as it applies to the particular circumstances of the home in heat and cold storage systems.
U.S. Pat. No. 3,812,903, for example, features a hot or cold storage system in which the hot or cold storage means is outside the living space, and air may be blown through a rock pile around a tank of liquid, thereby to absorb or release heat from or into the storage space before being circulated into the living space or back through a furnace or refrigeration coil. A disadvantage of this system is that since radiant heat transfer is not provided, its operation depends upon a blower. Another disadvantage is there are inevitable losses of heat or cold into the bottom and the sides of the heat storage pit. Yet another disadvantage of the system is that efficient means are not provided for utilizing available controlled heat sources such as fireplaces, incinerators, ovens and the like.
In recent years, fireplaces have been improved to some extent in efficiency as an immediate source of heat. Warm air circulation systems have been provided whereby a large measure of the heat potential is circulated to the living space of a shelter. Further improvements in fireplace efficiency have not been sought because without heat storage facilities, additional heat served no useful purpose. Present day heat storage facilities do not lend themselves to the utilization of this major home controlled heat source, nor has it been proposed to store such heat.
There also has been a need for integrating other common household heat sources into a central heating and air conditioning system.
Other qualities lacking in heat and cold storage facilities of the prior art include immediate utilization and cut-off. Many households are inhabited intermittently with families at work or in school during working hours of the day. For the ultimate in conservation, a heating system should be immediately responsive to heat requirements, and a cut-off should be immediately effective. Delayed resonse, characteristic of most present day heating and cooling systems, is not conducive to cut-off during periods of non-use. Radiant heat is immediately effective, and a heat storage unit placed in direct radiant heat transfer relationship with the living space would have immediate effect. When the radiant heat transfer relationship is terminated, heat loss from the heat storage unit would cease without transmission line loss.
All of the above considerations would indicate that a liquid storage system should be located in direct heat transfer relationship with the living space; but there are other considerations which must be accounted for in the design of a practical solar or weather-sensitive system. According to the present state of the art, the most practical method of air conditioning using solar heat is the absorption chiller, which, as is well known in the art comprises a lithium bromide absorber/condenser, a generator and an evaporator. Hot water is fed into the generator causing evaporation with resulting cooling. In order to employ such an air conditioning system it is necessary to have a supply of hot liquid. Of course the hot liquid supply in a solar system may come directly from the solar collectors; but if no storage capacity of hot (liquid) or of cold (liquid) is provided, there would be no carryover capacity from afternoon until morning or during other periods in which the solar collectors were not collecting heat. A system is needed, therefore, in which an integration of the needs of both summer and winter heating is provided.
A substantial difference in the requirements between the amount of storage needed for summer and winter operation of a heating system should be noted. Cold weather operation requires the maximum carryover capacity, (e.g., maximum heat storage), but not necessarily the highest possible temperature of the liquid in storage. Hot weather operation, on the other hand, requires liquid in storage at a higher temperature (in order to operate present day absorption chillers) but not, ordinarily, more of such liquid than is needed to carry over from one day to the next, that is to say, through the night. An ideal system would be provided for a long winter carryover with high versatility, and a much shorter summer carryover capacity, but at higher temperatures.
Prior art heat storage units, not designed for use in combination with solar systems have provided for control of heat transfer between storage and the living space, with removable insulation as in U.S. Pat. No. 2,066,127 but such devices were without recognition of or means for full adjustment of the storage-to-living space heat transfer independent of the controlled heat source for heating to storage medium.
For example, if the doors were opened most of the controlled heat, if in operation, was directed to the living space, this being inconsistent with an object of the instant invention to permit massive low temperature radiant heat transfer even where controlled (high temperature) heat is applied to the liquid storage medium. This means that in effect there would be a substantial loss (through regulation of overall heat emission) of massive low temperature radiant heat transfer from heat storage to living space while employing the controlled heat source. During this period of employment of controlled heat there would exist the uneconomical concentration of high temperature emission along with the necessity of shifting the adjustment of insulation whenever the need existed for use of the controlled heat source. Conversely where an open fireplace is employed as the controlled heat source it would sometimes be desirable in a solar system to use all of the direct radiant heat of the fireplace for its cheery effect but to conserve a substantial portion of the amount of the heat in storage whenever practical to do so.